1. Field of the Invention
The present invention relates to an electronic device such as an electron source formed on an insulating substrate and provided with a resistance film for preventing a surface of the insulating substrate from being charged.
2. Related Background Art
In recent years, a variety of electronic devices such as a semiconductor device and an electron-emitting device are utilized in various fields. Of those, an application of the electron-emitting device to an image display apparatus is being under study. The electron-emitting devices are roughly classified into two known types, i.e., one using a thermionic emission device and one using a cold cathode electron-emitting device. Examples of the cold cathode electron-emitting device include: a field emission type (hereinafter, referred to as FE type) device; a metal/insulating layer/metal type (hereinafter, referred to as MIM type) device; and a surface conduction electron-emitting device. The surface conduction electron-emitting device has a simple structure and is easy to manufacture. Thus, its application to the image display apparatus is greatly expected.
Those electronic devices are formed on the insulating substrate such as a glass substrate in some cases. In such cases, there arises a problem in that the surface of the insulating substrate is charged while the electronic device operates, so that operation conditions of the electronic device may be altered or become unstable. To solve the problem, disclosed in, for example, EP 343645 A (Japanese Patent Application Laid-Open No. 01-298624) and Japanese Patent Application Laid-Open No. 08-180801 is formation of a high-resistance electroconductive film on the insulating substrate surface.
The surface of the insulating substrate having the electronic device formed thereon is coated with a resistance film, making it possible to prevent the insulating substrate surface from being charged. Meanwhile, a current flowing through the resistance film causes an increase in total power consumption of the entire electronic device. In contrast, when placing an emphasis on a reduction in power consumption, the substrate is not sufficiently prevented from being charged. Thus, further improvements are required for achieving both the reduced power consumption and the prevention of the charging. In particular, in the surface conduction electron-emitting device having an electron-emitting region on the substrate surface, a shape of an antistatic resistance film in the electron-emitting region and its vicinities gives a large influence on electron-emitting characteristics. Thus, it is necessary to pay utmost attention to the formation of the resistance film. In addition, in the case of the surface conduction electron-emitting device, as described in the above publications, an energization operation called a forming process is carried out in forming the electron-emitting region. The inventors of the present invention have confirmed that the electron-emitting region is not formed favorably in this process, depending on the shape of the antistatic resistance film. As a result, an undesirable leak current is increased as well as an electron emission amount is decreased. Also, the above problem is not caused exclusively in the surface conduction electron-emitting devices, i.e., electron-emitting devices other than the surface conduction electron-emitting devices encounter the problem in some cases. Therefore, further improvements are demanded in this regard.